DESCRIPTION (Investigator's Abstract): The investigators propose to identify hospitalized elderly patients who are likely to suffer complications of their illnesses due to protein calorie undernutrition (PCU). Current methods of nutritional assessment are not adequate for identifying elderly medical patients at risk of nutritionally related complications because concurrent illnesses, age-related changes in objective measures, cognitive impairments of patients, and severity of underlying diseases were not incorporated in development of assessment methods but confound their application.The study will include the model of nutritionally related complications in a prospective cohort study of hospitalized elderly medical service patients, with blinded outcome assessment. The investigators extend the scope of nutrition related risk from the usual nosocomial complications to include prolongation of illness, complications acquired after discharge, worsening of health conditions present prior to admission, and reduced physical function. The study will utilize promising objective measures compiled from the pilot studies and the literature, common clinical methods (Subjective Global Assessment), and currently used objective parameters and indices (Nutritional Risk Index, Prognostic Nutritional Index). The investigators will measure non- nutritional factors that may confound assessment, including mental status examination, plasma volume, and severity of underlying disease. Patients will be assessed on admission and then followed during and after their hospitalizations for the development of nutritionally-related complications within 30 days of admission. The ability of current methods to identify nutritional risk will be assessed using standard methods for diagnostic tests (ROC curve analysis, likelihood ratios), after adjusting for non- nutritional risk factors. Using regression techniques, the investigators will identify combinations of clinical parameters that best identify risk for nutritionally related complications, after adjusting for non- nutritional risk factors. The investigators intend to express the results as simple, clinically applicable criteria. This project will lay the foundation for validation studies of identified nutritional criteria, and for a clinical trial to determine how much nutrition-related risks of complications can be reduced with appropriate nutritional support.